The present invention relates to a piezoelectric/electrostrictive device having a movable portion which operates on the basis of displacement of a piezoelectric/electrostrictive element, or a piezoelectric/electrostrictive device which can detect displacement of a movable portion by a piezoelectric/electrostrictive element, and particularly relates to a piezoelectric/electrostrictive device which is excellent in strength, impact resistance, and moisture resistance and has a high amplitude efficiency and can largely operate the movable portion.
Recently, in the fields of optical and magnetic recording, precisionmachining or the like, a displacement element which can adjust an optical path length or a position in sub-micron precision has been required, and the development of a displacement element which uses displacement based on the inverse piezoelectric effect or electrostrictive effect caused when voltage is applied to a piezoelectric/electrostrictive material (for example, a ferroelectric substance) has been progressed.
For example, as shown in FIG. 2, a piezoelectric actuator 21 is disclosed in Japanese Patent Laid-Open No. 10-136665, in which a fixed portion 25, a movable portion 24, and a beam portion 26 for connecting these portions are unitarily formed by providing a hole portion 28 in a plate-like substance made of a piezo electric/electrostrictive material and further, an electrode layer 22 is provided to the beam portion 26.
In the actuator 21, when voltage is applied to the electrode layer 22, the beam portion 26 expands and contracts in the direction of connecting the fixed portion 25 and the movable portion 24 by the inverse piezoelectric effect or electrostrictive effect, and therefore, it is possible to displace the movable portion 24 by arc-like displacement or rotary displacement in the plane of the plate-like substance.
However, in the actuator 21, since displacement in the expanding and contracting direction of a piezoelectric/electro-strictive material (that is, in the direction in the plane of the plate-like substance) is transmitted to the movable portion as it is, displacement of the movable portion 24 is rather small.
Furthermore, in the actuator 21, since all parts are constituted by a piezoelectric/electrostrictive material which is a brittle and relatively heavy material, there has been a problem in that the actuator 21 itself is heavy and it may easily be affected by a harmful vibration in operation (for example, a residual vibration or a noise vibration in high speed operation). In addition, the material has low mechanical strength and is inferior in handling efficiency, impact resistance, and moisture resistance.
In the actuator 21, in order to solve the above problems, it has been proposed to fill the hole portion 28 with a filler having flexibility, but it is clear that the efficiency of displacement based on the inverse piezoelectric effect or electrostrictive effect is lowered in the case of using fillers.
The present invention is made due to such problems of the prior art, and it is an object thereof to provide a displacement element in which a movable portion can largely be operated and is not affected by a harmful vibration in operation, and, additionally, has excellent mechanical strength, handling efficiency, impact resistance, and moisture resistance. As a result, the sensor element can detect a vibration of the movable portion accurately.